Page:Theophrastus - History of Stones - Hill (1774).djvu/347

 Melted with Zink, they make an uniform Mas of a fine gold Colour, as they do Bras with Calamine.

Held over melted Orpiment, they become not only white but brittle.

And by extreme Violence of Fire, are converted into a hard, dene, glay Matter, of a deep Red; tranparent, and in ome Degree reembling the Sorane Garnet.

It has been the general Opinion of the Chemits, that Solutions of this Metal in Acids were green, and in Alkalies blue: Some, however have altered, from a few Experiments of their own, or perhaps only from what they imagined mut have been the Succes of Experiments, this general Account; and particularly among certain of the more modern Writers, it has tood, that Copper, diolved in Acids or fixed Alkalies, affords a green Colour; and in volatile Alkalies, a fine Blue: But you will oberve, by the following Experiments, that thee Accounts are neither of them to be depended on: And, indeed, whoever has Diquiitions of this Kind to attempt, will always find, that it mut be a Knowledge of Nature, and not of Books, that will afford him what he can depend on; and that Sytems built on any Body's Experiments but his own, will be found to tand on a very infirm Bais.

What I have been able to learn, by repeated Experiments on this Metal in Mentrums of all Kinds, is, that the Solutions of it in different Fluids, cannot be, in regard to Colour, determinately